rx: always use/protect the xdr routines in the kernel

rx: always use/protect the xdr routines in the kernel

This clears up some warnings about duplicate symbols with Solaris 11
since the Solaris kernel already has these routines.  Since we never
use stock kernel version of the xdr routines perhaps we should always
use/protect our version of the symbols.

Reviewed-on: http://gerrit.openafs.org/4252
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 8336d31ac5092a16cfb206707e69c19f07f99241)

Change-Id: Iebf4470f5ddfc591f52f51d1d080bd58d11683a8
Reviewed-on: http://gerrit.openafs.org/4682
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>